CD4 and infection: Following infection with lymphocytic choriomeningitis virus (LCMV), small numbers of adoptively transferred SMARTA TCR transgenic T cells, which are specific for a LCMV glycoprotein epitope (GP61–80), responded in a manner that mirrored the functionality, kinetics, effector differentiation, and memory development of polyclonal endogenous CD4+ responders to the same peptide in the same host.